Nafion-mesoporous silica composite electrolyte: properties and direct ethanol fuel cells performance

Nafion-mesoporous silica composites were investigated aiming at improved performance of direct ethanol fuel cells (DEFC) operating at high temperature. Mesoporous silica (MPS) was synthesized by a sol-gel technique and added as the inorganic filler into Nafion membranes by casting process. The performance of DEFC using both Nafion and Nafion-MPS composites were evaluated by polarization curves and correlated to the electrical and structural properties of the electrolytes in ethanol environment inferred by impedance spectroscopy and small angle X-ray scattering, respectively. The main results show that Nafion-MPS composite electrolytes exhibit improved performance that was related to a structural pining of the ionic clusters of ethanol-saturated Nafion by the inorganic particles, which resulted in higher proton conductivity of the composite. The experimental results evidenced the relevance of a better understanding of the properties of Nafion-based electrolytes to further develop the direct alcohol fuel cells technology. (AU)